Google said that its advertising business was forced to block roughly 134 million malicious and misleading submissions last year.
The company reported that its volume of disapproved advertisements more than doubled between 2010 and 2011, up from 56.4 million blocks in 2010 and just 25.3 million in 2008. Additionally, Google banned some 824,000 advertisers in 2011, up from 248,000 in 2010 and 18,000 in 2008.
Google said that the advertisements were removed for violating the terms and conditions of the Google and AdSense platforms. The terms prohibits ads which are misleading, linked to malware attacks and considered to be spam.
"Bad ads have a disproportionately negative effect on our users; even a single bad ad slipping through our defenses is one too many," Google director of advertising engineering David Baker said in a blog post.
"That’s why we’re constantly working to improve our systems and utilise new techniques to prevent bad ads from appearing on Google and our partner sites."
Malicious advertisements have long been an issue for Google and other online advertising firms. Cybercriminals often embed malicious code or other unwanted content within advertising materials in order to bypass security protections and filtering systems.
Baker noted that the company has also had to ban advertisers for copyright and trademark violations, such as advertisements for counterfeit items.
"We find that there are relatively few malicious players, who make multiple attempts to bypass our defences to defraud users," said Baker.
"As we get better and faster at catching these advertisers, they redouble their efforts and create more accounts at an even faster rate."